Adjustment device for a hydrostatic piston machine, and hydrostatic axial piston machine

Abstract

An adjustment device for regulating the torque of a hydrostatic piston machine with adjustable swept volume, comprises an adjustment piston delimiting an adjustment chamber, a regulation valve defining a valve bore and including a valve slide positioned in the valve bore that controls inflow and outflow of pressure medium, and first and second feedback springs configured to exert feedback force on the valve slide in first and second displacement directions dependent on a position of the adjustment piston. The device further includes a regulation spring configured to exert a force on the valve slide in a second displacement direction. During an adjustment of the adjustment piston in a direction of maximum swept volume of the piston machine, beyond a particular position of the adjustment piston, the first and second feedback springs exert an increased force on the valve slide determined only by a spring constant of the first feedback spring.

What is claimed is: 
     
       1. An adjustment device for regulating torque of a hydrostatic piston machine with an adjustable swept volume, comprising:
 an adjustment piston delimiting an adjustment chamber; 
 a regulation valve defining a valve bore and including a valve slide positioned in the valve bore, the valve slide configured to control inflow of a pressure medium into the adjustment chamber and outflow of the pressure medium out of the adjustment chamber, the valve slide defining a measurement surface configured to be acted on by an operating pressure of the pressure medium of the piston machine in a first displacement direction; 
 a spring bearing at least partially located in the adjustment chamber and configured to bear against the valve slide; 
 a first feedback spring located within the adjustment chamber and configured to bear against the spring bearing and the adjustment piston; 
 a second feedback spring located within the adjustment chamber; and 
 a regulation spring configured to exert a force on the valve slide in a second displacement direction opposite to the first displacement direction, 
 wherein during an adjustment of the adjustment piston in a direction of minimum swept volume of the piston machine, beyond a particular position of the adjustment piston, the first feedback spring exerts a first feedback force on the valve slide and the second feedback spring is positioned in contact with the adjustment piston and the spring bearing to exert a second feedback force on the valve slide, and 
 wherein during an adjustment of the adjustment piston in a direction of maximum swept volume of the piston machine, beyond the particular position of the adjustment piston, the first feedback spring exerts the first feedback force on the valve slide and the second feedback spring is spaced apart from at least one of the adjustment piston and the valve slide to prevent the second feedback spring from exerting the second feedback force, 
 wherein the first feedback force is in the first displacement direction and the second feedback force is in the second displacement direction, and 
 wherein the direction of minimum swept volume of the piston machine is opposite of the direction of maximum swept volume of the piston machine. 
 
     
     
       2. The adjustment device according to  claim 1 , wherein a spacing is defined between the adjustment piston and the valve slide, the spacing being smallest when the adjustment piston is at a position corresponding to the maximum swept volume of the piston machine, and the spacing being greatest when the adjustment piston is at a position corresponding to the minimum swept volume of the piston machine. 
     
     
       3. The adjustment device according to  claim 1 , wherein the second feedback spring is positioned such that, over a first partial travel of the adjustment piston, the second feedback spring exerts the second feedback force counter to the first feedback force of the first feedback spring, and over a second partial travel of the adjustment piston, the second feedback spring is fully relaxed and is prevented from exerting the second feedback force. 
     
     
       4. The adjustment device according to  claim 3 , wherein the first feedback spring and the second feedback spring are positioned between the adjustment piston and the spring bearing such that over the first partial travel of the adjustment piston, the first feedback spring exerts the first feedback force in the first displacement direction on the spring bearing and the second feedback spring exerts the second feedback force in the second displacement direction on the spring bearing. 
     
     
       5. The adjustment device according to  claim 4 , further comprising:
 a retention part positioned in the adjustment piston, 
 wherein the first feedback spring is supported on the adjustment piston directly and the second feedback spring is supported on the adjustment piston via the retention part. 
 
     
     
       6. The adjustment device according to  claim 5 , wherein the retention part is a circlip positioned in the adjustment piston. 
     
     
       7. The adjustment device according to  claim 5 , wherein the retention part is a central projection located in the adjustment piston and extending through the spring bearing. 
     
     
       8. The adjustment device according to  claim 1 , wherein:
 the spring bearing is a bushing with an inner support surface positioned in engagement with the first feedback spring and an outer support surface positioned in engagement with the second feedback spring; and 
 a distance defined between the outer support surface and an end of the spring bearing that bears against the valve slide is greater than a distance defined between the inner support surface and the end of the spring bearing that bears against the valve slide. 
 
     
     
       9. The adjustment device according to  claim 8 , wherein the second feedback spring is positioned outside of the bushing. 
     
     
       10. The adjustment device according to  claim 8 , wherein the second feedback spring is positioned inside of the bushing. 
     
     
       11. The adjustment device according  claim 1 , wherein:
 the second feedback force exerted on the valve slide by the second feedback spring is additive to the first feedback force exerted on the valve slide by the first feedback spring; and 
 the second feedback force exerted on the valve slide by the second feedback spring remains constant during the adjustment of the position of the adjustment piston in the direction towards the position of the adjustment piston corresponding to the maximum swept volume of the piston machine beyond the particular position of the adjustment piston. 
 
     
     
       12. The adjustment device according to  claim 11 , further comprising:
 a stop part; and 
 a support spring, 
 wherein the second feedback spring is braced between the spring bearing and the stop part; 
 wherein the support spring is braced between the stop part and the adjustment piston; and 
 wherein the stop part is prevented from further movement beyond another particular position of the adjustment piston. 
 
     
     
       13. The adjustment device according to  claim 12 , wherein, in the another particular position of the adjustment piston, the stop part abuts against a housing of the regulation valve. 
     
     
       14. The adjustment device according to  claim 1 , further comprising:
 a compensation surface, 
 wherein the valve bore is open toward the adjustment chamber such that the valve slide, at a face side facing toward the adjustment chamber, is loaded in the first displacement direction by an adjustment pressure; 
 wherein the compensation surface is at least as large as the face side facing toward the adjustment chamber that is loaded by the adjustment pressure in the first displacement direction; and 
 wherein the adjustment pressure generates a force acting on the valve slide in the second displacement direction. 
 
     
     
       15. The adjustment device according to  claim 1 , further comprising:
 a pressure medium inflow duct, 
 wherein the valve slide has an annular groove via which, as a result of displacement of the valve slide from a regulation position in a first direction, a first fluidic connection is formed between the adjustment chamber and the pressure medium inflow duct, and as a result of displacement of the valve slide from the regulation position in an opposite direction, a second fluidic connection is formed between the adjustment chamber and a pressure medium outflow duct. 
 
     
     
       16. An-adjustment device for regulating torque of a hydrostatic piston machine with an adjustable swept volume, comprising:
 an adjustment piston delimiting an adjustment chamber; 
 a regulation valve defining a valve bore and including a valve slide positioned in the valve bore, the valve slide configured to control inflow of a pressure medium into the adjustment chamber and outflow of the pressure medium out of the adjustment chamber, the valve slide defining a measurement surface configured to be acted on by an operating pressure of the pressure medium of the piston machine in a first displacement direction; 
 a first feedback spring and a second feedback spring located in the adjustment chamber, at least one of the first feedback spring and the second feedback spring exerts a feedback force on the valve slide depending a position of the adjustment piston; 
 a regulation spring configured to exert a force on the valve slide in a second displacement direction opposite to the first displacement direction; 
 a pressure medium inflow duct; 
 an axial bore which opens out at a face side of the valve slide, 
 wherein during an adjustment of the adjustment piston in a direction of maximum swept volume of the piston machine, beyond a particular position of the adjustment piston, only the first feedback spring exerts the feedback force on the valve slide, 
 wherein the valve slide has an annular groove via which, as a result of displacement of the valve slide from a regulation position in a first direction, a first fluidic connection is formed between the adjustment chamber and the pressure medium inflow duct, and as a result of displacement of the valve slide from the regulation position in an opposite direction, a second fluidic connection is formed between the adjustment chamber and a pressure medium outflow duct, 
 a transverse bore which opens out in the annular groove; and 
 wherein the transverse bore and the axial bore are in a fluidic connection between the annular groove of the valve slide and the adjustment chamber. 
 
     
     
       17. The adjustment device according to  claim 16 , wherein a cross section of the transverse bore is smaller than a cross section of the axial bore. 
     
     
       18. A hydrostatic axial piston machine, comprising:
 a housing; 
 a drive unit including a cylinder drum, a drive shaft, and a pivot cradle, the drive unit positioned in the housing; 
 a plurality of displacement pistons positioned in the cylinder drum; and 
 an adjustment device configured to regulate torque of the piston machine with an adjustable swept volume, including:
 an adjustment piston delimiting an adjustment chamber; 
 a regulation valve defining a valve bore and including a valve slide positioned in the valve bore, the valve slide configured to control inflow of a pressure medium into the adjustment chamber and outflow of the pressure medium out of the adjustment chamber, the valve slide defining a measurement surface configured to be acted on by an operating pressure of the pressure medium of the piston machine in a first displacement direction; 
 a spring bearing at least partially located in the adjustment chamber and configured to bear against the valve slide; 
 a first feedback spring located within the adjustment chamber and configured to bear against the spring bearing and the adjustment piston; 
 a second feedback spring located within the adjustment chamber; and 
 a regulation spring configured to exert a force on the valve slide in a second displacement direction opposite to the first displacement direction, 
 
 wherein during an adjustment of the adjustment piston in a direction of minimum swept volume of the piston machine, beyond a particular position of the adjustment piston, the first feedback spring exerts a first feedback force on the valve slide and the second feedback spring is positioned in contact with the adjustment piston and the spring bearing to exert a second feedback force on the valve slide, 
 wherein during an adjustment of the adjustment piston in a direction of maximum swept volume of the piston machine, beyond the particular position of the adjustment piston, the first feedback spring exerts the first feedback force on the valve slide and the second feedback spring is spaced apart from at least one of the adjustment piston and the valve slide to prevent the second feedback spring from exerting the second feedback force, 
 wherein the first feedback force is in the first displacement direction and the second feedback force is in the second displacement direction, and 
 wherein the direction of minimum swept volume of the piston machine is opposite of the direction of maximum swept volume of the piston machine.